Field of Invention
The present invention relates to a micro-electro-mechanical system (MEMS) device, in particular a MEMS device including a proof mass with an inner extension portion, whereby the MEMS device has a higher sensitivity but does not require a linkage.
Description of Related Art
MEMS devices are commonly used nowadays, and one common application of the MEMS device is for motion sensing. FIG. 1 shows a prior art MEMS device 10 disclosed by U.S. Pat. No. 6,892,576, wherein only one fourth of the MEMS device 10 is shown in the figure (the MEMS device 10 has a symmetric structure). The proof mass 11 is connected to a substrate (not shown) through springs 12, linkages 13, and anchors 14. The linkages 13 are connected to the substrate by multiple anchors 14, for avoiding distortion of the linkages 13. In this prior art, the linkages 13 which are provided for connecting the springs 12 occupy a large area, so the boundary size of the proof mass 11 needs to increase to obtain the required mass quantity. Hence, the MEMS device 10 needs a larger area and its size can not be reduced. Further, the structure of multiple anchors also increases the complexity of the manufacturing process.
FIG. 2 shows another prior art MEMS device 20 disclosed by U.S. Pat. No. 8,393,215, wherein a proof mass 21 is connected to a substrate 25 through springs 22, linkages 23, and anchors 23. The linkages 23 for connecting the springs 22 occupy a large area, so the boundary size of the proof mass 11 needs to increase to obtain the required mass quantity. Besides the aforementioned demerits, the lengths of the linkages 23 may deviate due to thermal deformation, and this may cause an offset of the proof mass to seriously affect the accuracy of the device.
In view of the demerits of the prior art, the present invention provides a MEMS device having at least one inner extension portion instead of linkages, to increase the sensitivity of the device.